Generally, in an automotive disk brake, the brake rotor is attached to the car by an axle. As the car travels, the brake rotor rotates with the wheel of the car. The brake caliper assembly contains the brake piston and brake pads and is rigidly mounted to the car frame. Upon application of the brake pedal, hydraulic fluid drives the brake piston or pistons outward from the cylinders in the caliper assembly forcing the brake pads to engage the rotor causing the frictional braking force that stops the car from traveling.
Since the discovery of the toxic effects of asbestos, brakes for light duty vehicles, such as pickup trucks and cars, have been made from cast iron rotors or drums engaged by brake pads or shoes having semi-metallic or non-asbestos organic composite pads. These brakes have suffered from problems such as noise, shudder, vibration and short lifetimes of the pads, rotors and drums. Drums and rotors have also tended to warp due to greater heat generation as a result of the use of semi-metallic brake pads. A consequence of this has been excessive warranty costs to automobile manufacturers, which has been estimated to be about $85 per car in North America.
In addition, since the present pads or shoes wear out quickly, the hydraulic brake piston that forces the pad into contact with the rotor or drum has needed to have a long travel to compensate for the wearing out of the brake pad or shoe (i.e., the pad has to be thicker to compensate for the faster wear rate). The long travel necessitates the use of a larger caliper assembly and larger piston, which adds weight to the brake. The excessive wear of today's brake pads also cause aesthetic problems, such as brake pad dust on the wheels.
More recent alternative brakes, such as carbon/carbon composite brakes, have only been used, due to cost and design considerations, on the most exotic applications (e.g., race cars and military aircraft).
Therefore, it would be desirable to provide a brake that is lighter, avoids the short lifetime, dusting and repair costs associated with today's light duty vehicle brakes at a cost competitive with current metal brakes.